1. Field of the Invention
The present invention relates to multi channel magnetic transducer heads, and more particularly to a thin film type magnetic transducer head manufactured using thin film forming technique.
2. Description of the Prior Art
Referring to FIGS. 1 through 4, a thin film type multi channel magnetic transducer head in the prior art, for example, that of electromagnetic induction type, comprises a magnetic substrate 1 made of magnetic ferrite, such as Mn-Zn ferrite or Ni-Zn ferrite, and a coil conductor 3 as a head winding formed on a main surface of the magnetic substrate 1 through an insulation film 2 of SiO.sub.2 or Si.sub.3 N.sub.4 with thickness 1 .mu.m. The coil conductor 3 is formed by U-shaped conductive layer of Al, Cu or Au. Although the example discloses the coil conductor in one turn, constitution of several turns in spiral or constitution of several turns in multi layer structure may be used. An insulation film 5 of SiO.sub.2 or Si.sub.3 N.sub.4 with thickness 1 .mu.m is formed on whole surface of the coil conductor 3, and a thin film magnetic core 4 crosses the coil conductor 3 through the insulation film 5 and front end of the thin film magnetic core 4 extends to a surface S faced to a magnetic recording medium. The thin film magnetic core 4 is formed by a magnetic thin film of sendust or permalloy having width 60 .mu.m and thickness 10 .mu.m. Rear end of the thin film magnetic core 4 passed through a window 6 bored on the insulation films 2 and 5 and is attached to the magnetic substrate 1 directly, for example, and magnetically connected to the substrate 1 in close connection. A non-magnetic gap spacer 7 with thickness 0.5 .mu.m to constitute an effective magnetic gap g is formed between the front end of the thin film magnetic core 4 and the magnetic substrate 1. Thus a magnetic circuit is constituted which includes the magnetic gap g with gap length specified by thickness of the gap spacer layer 7 and forms a closed magnetic circuit in co-operation of the thin film magnetic core 4 and the magnetic substrate 1, and a magnetic head element h is provided with the coil conductor 3 crossing the magnetic circuit. A plurality of magnetic head elements h in such constitution are arranged at the predetermined number in common use of the magnetic substrate 1, and each magnetic gap g is faced to the common surface S facing to the magnetic recording medium at a predetermined track interval. Wherein FIG. 1 is a plan view of the head; FIG. 2 is a side view of FIG. 1; FIG. 3 is a sectional view taken in line III--III of FIG. 1; and FIG. 4 is a sectional view taken in line IV--IV of FIG. 1.
Process of manufacturing such a multi element thin film magnetic head will now be described. First, a magnetic substrate 1 is coated by an insulation film 2 as shown in FIG. 5. A coil conductor 3 is arranged on a predetermined position of the insulation film 2, and an insulation film 5 is applied to whole surface including that on the coil conductor 3 as shown in FIG. 6. Part of the insulation films 2 and 5, where a gap spacer layer 7 as hereinbefore described is to be formed, is selectively removed at a predetermined width along front side edge of the substrate 1, i.e. at width d corresponding to gap depth of the magnetic gap g to be formed finally, by etching using a photolithography as shown in a sectional view of FIG. 7 and a plan view of FIG. 8. The removed portion of the insulation films 2 and 5 is coated with a non-magnetic gap spacer layer 7 of a predetermined thickness, i.e. thickness corresponding to gap length of the magnetic gap g, such as thickness 0.5 .mu.m as shown in FIG. 9. A window 6 is bored on the insulation films 2 and 5 and a magnetic thin film 4' of sendust or permalloy to constitute a magnetic core is formed on whole surface by means of sputtering as shown in FIG. 10. Unnecessary portion of the thin film 4' is removed by etching using a photolithography and the thin film magnetic core 4 of predetermined pattern is formed as shown in FIG. 11 and described referring to FIGS. 1 through 4.
In above described process, the thin film magnetic cores 4 regarding various tracks are formed simultaneously. In this case, since the magnetic core 4 hence the magnetic thin film 4' must have magnetic resistance of the magnetic circuit being as small as possible, thickness thereof is selected as large as possible, for example, to 10 .mu.m. Therefore, during patterning of the magnetic thin film 4', i.e, etching using a photolithography, the etching progresses not only in thickness direction of the magnetic thin film 4' but also in surface direction. That is, so-called side etching is occured thereby edge of the pattern has trailing shape. As shown in FIG. 3 trailing portions a and b are produced on both sides of the magnetic gap g regarding the track width direction, thereby the track width of the magnetic gap g cannot be determined accurately but variation occurs. In the case of multi tracks, the etching is not performed well but the thin film magnetic cores 4 of various tracks may be magnetically connected with each other by thin layer of the magnetic film. Particularly, as the guard band width as the track spacing becomes narrow, this problem is accelerated. If the track width cannot be determined accurately, the high density recording as original object of the thin film magnetic transducer head cannot be attained but serious problem in characteristics may occur. Moreover, good magnetic recording cannot be performed.